wnd_main = {}

function wnd_main.show()
    if wnd_main._wnd then
        wnd_main._wnd:CenterWindow()
        wnd_main._wnd:ShowWindow()
        return
    end

    local wnd = SD.NewWindow(T"wnd_main")
    if wnd then
        local wndparam = {
            title = T"title",
            style= ED_FRAME,
            exStyle = ED_EX_TOPMOST | ED_EX_TOOLTIP
        }
        if wnd:Create(wndparam) then
            wnd:CenterWindow()
            wnd:ShowWindow()
        end
    end

    wnd_main._wnd = wnd
end